1. Field of the Invention
The present invention relates to an antenna, and particularly to a broadband couple-fed planar antenna with coupled radiating strips electrically connected to a ground plane.
2. Description of the Related Art
In the field of wireless communication systems, it is very important to develop small and low profile antennas for the miniaturization of communication equipment. Various types of the inverted-F antennas have been proposed for this application, because they are compact in their dimensions, easy to manufacture, and exhibit good electrical performance. The inverted F antenna allows a simple impedance match in a low-profile.
FIG. 1 (PRIOR ART) is the exploded view of a conventional aperture coupled microstrip antenna. As shown in FIG. 1, the aperture coupled microstrip antenna 100 includes a ground plane 110 with a aperture 111, a feeding microstrip 101 placed at one side of the ground plane 110, and a patch 120 placed at the opposite side of the ground plane 110. This antenna demonstrates a stacked configuration, exhibiting a relatively complicated structure. The dimensions of the feeding microstrip 101 and the aperture 111 should be properly designed. The dimensions of the patch 120, the radiator, are determined by the half-wavelength resonance. Therefore, for the application of bluetooth and wireless local area network (WLAN), the dimensions of the aperture coupled microstrip antenna are relatively large and thus take up space.
FIG. 2 (PRIOR ART) shows a planar inverted-F antenna with a length of approximate quarter wavelength. The planar inverted-F antenna 200 includes a patch 220, a ground plane 210, a short strip 230, and a feeding line 201. The disadvantage of the planar inverted-F antenna 200 is that it requires a short strip or short pin.
FIG. 3 (PRIOR ART) shows another planar inverted-F antenna with a direct feeding microstrip. The inverted-F antenna 300 includes a inverted-F strip 301, a ground plane 310, a metal plane 340, and via holes 330. The disadvantage of the inverted-F antenna 300 is that it requires via holes. The via holes 330 are employed in the structure to connect electrically the ground plane 310 and the metal plane 340.
A significant problem with the inverted-F antennas mentioned above is that extra fabrication processes are required.
Usually, the conventional inverted-F antenna has relatively narrow bandwidth. It is not flexible to broaden the conventional inverted-F antenna bandwidth.
A compact antenna which is broadband and compatible with PCB structure is needed.
Therefore, an object of the present invention is to provide a broadband couple-fed planar antenna, which has an flexible design in operating bandwidth and a high compatibility with PCB structure.
The present invention achieves the above-indicated objects by providing a first type of the broadband couple-fed planar antenna. It comprises one grounded radiators, electrically connected to a ground plane, having a first segment extended from an edge of the ground plane and a second segment bending at an angle, and a feeding line disposed above the ground plane and extended from the edge the ground plane and parallel to the first segment of the grounded radiator.
The present invention achieves the above-indicated objects by providing a second type of the broadband couple-fed planar antenna. It comprises two grounded radiators, electrically connected to a ground plane, having a first segment extended from an edge of the ground plane and a second segment bending at an angle, and a feeding line disposed above the ground plane and extended from the edge the ground plane and parallel to the first segment of the grounded radiators.
These two grounded radiators broaden the bandwidth of the antenna.
The present invention also discloses a third type of broadband couple-fed antenna. It comprises three grounded radiators, electrically connected to a ground plane, having a first segment extended from an edge of the ground plane and a second segment bending at an angle, and a feeding microstrip line disposed above the ground plane and extended from the edge of the ground plane and parallel to the first segment of the grounded radiators.
These three grounded radiators achieve an even broad bandwidth.